Systems and devices for dynamic processing of optical signals

ABSTRACT

Optical systems are disclosed which include one or more components such as an optical multiplexer, an optical demultiplexer, and, an optical amplifier. An optical device is included in the optical system and is configured to communicate with the optical component(s). The optical device includes a substrate proximate to which is disposed a first waveguide array. A second waveguide array is also provided that is disposed proximate the substrate so that a portion of the second waveguide array intersects a portion of the first waveguide array at a predetermined angle, so that a junction is formed. An index of refraction associated with the junction can be varied so that desirable effects can be implemented concerning optical signals transmitted through the waveguides.

RELATED APPLICATIONS

This application is a continuation, and claims the benefit, of U.S.patent application Ser. No. 10/098,050, entitled DYNAMIC VARIABLEOPTICAL ATTENUATOR AND VARIABLE OPTICAL TAP, filed Mar. 14, 2002, which,in turn, claims the benefit of the following three applications, namely:Ser. No. 60/276,182, entitled MINIATURIZED RECONFIGURABLE DWDM ADD/DROPSYSTEM FOR OPTICAL COMMUNICATION SYSTEM, and filed Mar. 15, 2001; Ser.No. 09/999,054, entitled N×N OPTICAL SWITCHING DEVICES BASED ONTHERMAL-OPTICS INDUCED TOTAL INTERNAL REFLECTION EFFECT, filed Nov. 1,2001 (claiming priority from Ser. No. 60/259,446, filed Jan. 2, 2001);and, Ser. No. 10/097,756, entitled COMBINED MULTIPLEXER ANDDEMULTIPLEXER FOR OPTICAL COMMUNICATIONS SYSTEMS, filed Mar. 14, 2002(claiming priority from Ser. No. 60/276,182, filed Mar. 15, 2001). Allof the aforementioned patent applications are incorporated herein intheir respective entireties by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to processing and manipulation ofoptical signals. More particularly, embodiments of the invention areconcerned with systems and devices for performing processes such asdynamic tapping, splitting or attenuation of optical signals.

2. Background of the Invention

Increased demand for data communication and growth of the internet haveresulted in increased demand for communication capability withinmetropolitan areas. There has also been an equally large increase indemand for communication capability between large metropolitan areas.Optical communication systems formed by networks of fiber optic cablesare being developed and installed to meet this increased demand.

Various types of optical switches and techniques are currently used incommunication systems and computer systems. Many currently availableoptical switches are based upon optoelectric and electrooptic conversionof light signals and electrical signals within the associated opticalswitch. One type of presently available optical switch includes a matrixof thermooptic switching elements interconnected by waveguides formed ona silica substrate. Switching of light signals is accomplished by theuse of thin film heaters to vary the temperature of the switchingelements. Electrical circuits are also provided to supply switchingcurrent to the heaters. A heat sink may be provided to dissipate heatcaused by the switching operations. One example of such switches isshown in U.S. Pat. No. 5,653,008.

Some presently available optical switches include a semiconductorsubstrate with vertical current flow to heat active regions of anassociated optical switch. One example of such switches is shown in U.S.Pat. No. 5,173,956. Some optical switches require mode perturbation togenerate required mode patterns for the desired switching function.Examples of such optical switches include directional couplers and MachZhender interferometers. Such optical switch designs often have poorscalability, relatively high manufacturing costs and low optical signalbandwidth.

Various types of optical signal amplifiers, wavelength divisiondemultiplexers, optical switches, wavelength division multiplexers andtechniques are currently used in optical communication systems. Opticalsignal amplifiers, wavelength division multiplexers and demultiplexersand other components associated with optical communication systemstypically function best when respective signal levels of associatedoptical signals are substantially equal with each other. A variation insignal level of multiple wavelength optical signals may result in anundesirable signal to noise ratio and resulting poor performance byswitches, amplifiers and other optical components.

Multiple wavelength optical signals are often collectively amplified bya light amplifier. The amplification factor of many light amplifiers isdependent upon the wavelength of each optical signal. Therefore,amplification factors for multiple wavelength optical signals often varydepending on the specific wavelength of each signal. The resultingdifference between signal levels of respective multiple wavelengthoptical signals amplified by a single amplifier is often relativelysmall. However, when a large number of light amplifiers (ten or more)are used in a fiber optic communication system, the variation in signallevels becomes cumulative and may result in unsatisfactory lowering ofassociated signal to noise ratios. Therefore, variable opticalattenuators are often provided at the input stage and/or output stage oflight amplifiers in both large metropolitan communication systems andlong distance fiber optic communication systems to adjust signal levelsof multiple wavelength light signals to maintain desired signal to noiseratios.

Variable optical attenuators are often included in optical communicationsystems to maintain a desired signal level for each optical signal orwavelength. Examples of variable optical attenuators (VOA) includenatural density filters which are often used to suppress the amount oflight depending on wavelength characteristics. Other variable opticalattenuators include mechanical devices which position a glass substrateso that light signals may be attenuated by varying the position of theglass substrate. Still other variable optical attenuators attenuatelight signals by rotating the polarization of each light signal as itpasses through a Faraday element.

Optical taps are also included in many optical communication systems tomonitor both performance of individual components and performance of theoverall system.

BRIEF SUMMARY OF AN EXEMPLARY EMBODIMENT OF THE INVENTION

In general, exemplary embodiments of the invention are concerned withvariable optical components and related systems. In one exemplaryimplementation, an optical system is disclosed that includes one or morecomponents such as an optical multiplexer, an optical demultiplexer,and, an optical amplifier. An optical device is included in the opticalsystem and is configured to communicate with the optical component(s).The optical device includes a substrate proximate to which is disposed afirst waveguide array. A second waveguide array is also provided that isdisposed proximate the substrate so that a portion of the secondwaveguide array intersects a portion of the first waveguide array at apredetermined angle, so that a junction is formed. An index ofrefraction associated with the junction can be varied so that desirableeffects can be implemented concerning optical signals transmittedthrough the waveguides.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, in which like referencenumbers indicate like features, and wherein:

FIG. 1 is a schematic drawing showing various components associated withan optical communication system including a plurality of amplifiers anddemultiplexers, a first backplane, a plurality of combined opticalswitches and dynamic variable optical attenuators, a second backplane, aplurality of multiplexers and amplifiers;

FIG. 2 is a schematic drawing showing a plan view with portions brokenaway of an 8×8 waveguide array formed in accordance with teachings ofthe present invention;

FIG. 3 is a schematic drawing in section with portions broken away takenshowing one example of waveguides formed on a substrate in accordancewith the teachings of the present invention;

FIG. 4 is a schematic drawing in section with portions broken away takenshowing another example of waveguides formed on a substrate inaccordance with the teachings of the present invention;

FIG. 5 is a schematic drawing in section with portions broken away takenshowing still another example of waveguides formed on a substrate inaccordance with teachings of the present invention;

FIG. 6 is a schematic drawing with portions broken away showing portionsof two waveguides and an electrode heater which may be used to form anoptical attenuator or an optical tap in accordance with teachings of thepresent invention;

FIG. 7 is a more detailed drawing showing a plan view with portionsbroken away of the two waveguides and electrode heater of FIG. 6;

FIG. 8 is a schematic drawing in section showing portions of the opticaldevice of FIG. 7;

FIG. 9 is a graph showing optical output or signal level versus time atan output port of a dynamic variable optical attenuator or a dynamicvariable optical tap formed in accordance with teachings of the presentinvention for a current flow through an associated electrode heater;

FIG. 10 is another graph showing attenuation of an optical signal at anoutput port of a dynamic variable optical attenuator or a dynamicvariable optical tap formed in accordance with teachings of the presentinvention;

FIG. 11 is a schematic drawing with portions broken away showing oneexample of a dynamic variable optical attenuator formed in accordancewith teachings of the present invention;

FIG. 12 is a schematic drawing in section with portions broken awayshowing another example of a dynamic variable optical attenuator formedin accordance with teachings of the present invention; and

FIG. 13 is a schematic drawing showing another embodiment of an opticalcommunication system which includes multiple dynamic variable opticalattenuators and/or dynamic variable optical taps formed in accordancewith teachings of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention and its advantages arebest understood by referring to FIGS. 1 through 13 of the drawings, likenumerals being used for like and corresponding parts of the variousdrawings.

The terms “optical signal or signals” and “light signal or signals”include all electromagnetic radiation which may satisfactorilycommunicate information through a waveguide and/or fiber optic cable. Anoptical tap or optical attenuator incorporating teachings of the presentinvention may be satisfactorily used with optical signals in theinfrared, visible and ultraviolet spectrum. The optical tap or opticalattenuator may be used with communication systems for digitalinformation and analog information.

Optical devices incorporating teachings of the present invention may besatisfactorily used to tap optical signals for various monitoringpurposes and to attenuate or reduce intensity of optical signals. Signallevel and intensity may also be referred to as “optical power.”

The term “waveguide” is used in this application to include the fullrange of optical signal conductors that may be satisfactorily used tocommunicate optical signals. A waveguide typically includes a coreformed from a first optical material and disposed in a channel formed ina second optical material. A fiber optic cable is one example of aspecific type of waveguide. However, waveguides satisfactory for usewith the present invention may have various configurations other thanfiber optic cables and cores disposed in a channel.

The terms “polymer” and “polymers” include any macromoleculecombinations formed by chemical union of multiple, substantiallyidentical combining units or monomers and have satisfactorycharacteristics for use as a waveguide for optical signals. Combinationsof two, three or four monomers are often referred to respectively asdimers, trimers, and tetramers. These combinations may be furtherclassified as inorganic, organic, natural, synthetic or semisynthetic.For purposes of this application, the terms “polymers and othercombinations of monomers” and “polymers or other combinations ofmonomers” means any combination of two or more monomers which may besatisfactorily used to form a waveguide in accordance with teachings ofthe present invention including, but not limited to, inorganic, organic,natural, synthetic and semisynthetic combinations.

A wide variety of polymers and other combinations of monomers may besatisfactorily used to form waveguides and optical devices in accordancewith teachings of the present invention. The following discussion ofsome examples of chemical compounds is illustrative only and is notintended to limit the scope of the present invention.

Various features of the present invention will be described with respectto an optical signal as it travels from input fiber optic cables 22 tooutput fiber optic cables 23 (see FIG. 1) and from the input end of awaveguide to the output end of a waveguide. (See FIGS. 11 and 12.)However, dynamic, variable optical attenuators and dynamic, variableoptical taps formed in accordance with teachings of the presentinvention may be satisfactorily used with a wide variety of opticalsignals, optical networks, optical communication systems and associatedwaveguides. The optical signals may carry digital information and/oranalog information.

Communication system 20, as shown in FIG. 1, includes a plurality offiber optic cables 22 and 23 and one or more switching centers 24.Communication system 20 may also include a wide variety of othercomponents associated with modern fiber optic communication networks.

Wavelength division multiplexing (WDM) techniques allow each fiber opticcable 22 and 23 to carry multiple optical signals at various wavelengthswhich substantially increases the efficiency of each fiber optic cable22 and 23. Recently, dense wavelength division multiplexing (DWDM)techniques have been developed to allow existing fiber optic networks tobetter satisfy increased demand for communication capabilities.

For purposes of describing various features of the present invention,switching center 24 will be described as having a plurality of inputfiber optic cables 22 designated as 22 a, 22 b, 22 c through 22 n and aplurality of output fiber optic cables 23 a designated as 23 a, 23 b, 23c through 23 n. Switching center 24 may have multiple optical switchassemblies 40. Optical switch assemblies 40 cooperate with each other toallow switching of a selected optical signal from one fiber optic cable22 to a selected fiber optic cable 23. Each optical switch assembly 40may include multiple optical attenuators and multiple optical tapsformed as integral components thereof in accordance with teachings ofthe present invention. Alternatively, switching center 24 may includeseparate optical switches and separate optical attenuators and tapsincorporating teachings of the present invention.

Each fiber optic cable 22 may be coupled with switching center 24through a respective amplifier 26 and dense wavelength division (DWD)demultiplexer 28. Backplane 30 is preferably provided to opticallycouple DWD demultiplexers 28 with optical switch assemblies 40. Eachoptical switch assembly 40 may include multiple dynamic variable opticalattenuators and multiple dynamic variable optical taps incorporatingteachings of the present invention. Backplane 32 is preferably providedto optically couple optical switch assemblies 40 with multiplexers 36and respective amplifiers 38. Each dense wavelength division multiplexer36 and associated amplifier 38 will direct selected optical signals tofiber optic cables 23.

In a typical wavelength division multiplexing system, the power level ofeach signal transmitted from a respective input fiber optic cable 22 toa respective output fiber optic cable 23 may vary significantly. Therespective power levels or signal levels of optical signals communicatedfrom optical switch assemblies 40 to backplane 32 are preferablyadjusted to avoid communication problems associated with multiplesignals at different power levels. Thus, one or more dynamic variableoptical attenuators incorporating teachings of the present invention maybe provided to reduce or adjust the signal level of the optical signalsto within a desired range.

Dynamic variable optical attenuators formed in accordance with teachingsof the present invention may be used to reduce or adjust the signallevel of the optical signals prior to entering backplane 32.Alternatively dynamic variable optical attenuators incorporatingteachings of the present invention may be used to reduce or adjust thesignal level of the optical signals after they exit from backplane 32.One of the technical benefits of the present invention includes theability to incorporate a dynamic variable optical attenuator and/or tapas an integral component of other optical devices associated withswitching center 24 or to form the dynamic, variable optical attenuatorsand/or taps as separate individual components associated with switchingcenter 24.

FIG. 2 is a schematic drawing showing a plan view of one example of anoptical device incorporating teachings of the present invention. Opticaldevice 140 may be used as an optical tap or as an optical splitter.Optical device 140 may also be used to form at least a portion of anoptical attenuator. An optical tap, optical splitter, or opticalattenuator may have dynamic, variable characteristics. For someapplications, optical device 140 as shown in FIG. 2 may also be used toform at least a portion of an optical switch. Optical switch assemblies40 may include multiple optical devices 140 which function as opticalswitches, optical attenuators and optical taps.

Optical device 140 preferably includes a first set or array ofwaveguides 50 and a second set or array of waveguides 60. For purposesof defining various features of the present invention the first array ofwaveguides 50 are numbered 51 through 58 and the second array 60 arenumbered 61 through 68. Each set or array of waveguides 50 and 60includes respective input ends “a” and output ends “b”.

Various features of the present invention will be described with respectto optical signals or light signals (not expressly shown) traveling frominput end (a) of waveguides 51–58 to the respective output end (b) ofwaveguides 51-a and/or 61–68. When optical device 140 functions as anoptical attenuator or an optical tap, optical signals or light signalswill generally only be supplied to input ends “a” of one of thewaveguide arrays (51–58 or 61–68). When optical device 140 is used tofunction as an optical switch, optical signals will often becommunicated with input ends “a” of both waveguides 51–58 and 61–68.

Waveguides 51 through 58 are preferably formed generally parallel witheach other on substrate 42. Waveguides 61 through 68 are also formedgenerally parallel with each other on substrate 42. For someapplications, first set of waveguides 50 and second set of waveguides 60preferably intersect with each other at a selected angle θ. Examples ofwaveguides 50 and 60 may be formed on substrate 42 are shown in FIGS. 3,4, and 5.

The angle θ defined by each intersection between the waveguides of firstarray 50 and second array 60 is preferably selected to be betweenapproximately two degrees (2°) and eight degrees (8°) depending upon themicrostructure of the material used to form the waveguides and theassociated index of refraction. For one application angle θ may beapproximately three degrees (3°). For other applications angle θ ispreferably approximately six degrees (6°). By forming optical device 140with an angle θ having a value between approximately two degrees toeight degrees, an optical signal may travel through respectivewaveguides 51 through 58 and 61 through 68 without any significantperturbation or reflection at the intersection or junction of thewaveguides unless the index of refraction at the junction is changed byheating. For other applications the index of refraction at the junctionmay be change by electrooptic, magnetooptic or acoustooptic effects.

Respective electrode heaters 80 are preferably disposed adjacent to eachintersection 70 of the first array of waveguides 50 with the secondarray of waveguides 60. Electrode heaters 80 may be formed from varioustypes of materials including nickel chrome alloys (NiCr), chromium gold(Cr/Au) and other metals and alloys. For purpose of illustration onlyone electrode heater 80 is shown in FIG. 2. Since first array 50 andsecond array 60 each have eight individual waveguides, optical device140 has a total of sixty-four (64) intersections or junctions 70 betweenwaveguides 51–58 and waveguides 61–68. Therefore, optical device 140will preferably have sixty-four (64) electrode heaters 80. Eachelectrode heater 80 may apply heat to its associated junction 70 todirect or deflect optical signals from an associated waveguide in firstarray 50 to an associated waveguide in second array 60.

A portion of each optical signal travelling from respective input end“a” of waveguides 51 through 58 may be directed to a respectivewaveguide in second array 60 using the appropriate electrode heater 80.Electrical current may be provided from an appropriate source such ascurrent source 82 formed on substrate 42. For the embodiment of thepresent invention as shown in FIG. 2, electrical current may flow fromsource 82 through lead 84, electrode 80 and return to ground 86 throughlead 88. Current source 82, leads 84 and 88, and ground 86 may be formedon substrate 42 using conventional semiconductor fabrication techniques.

As previously noted optical device 140 may be used as an optical tap.For example, electrical current may be provided to associated electrodeheater 80 to direct a portion of an optical signal traveling throughwaveguide 58 to waveguide 61. Varying the amount of electrical currentsupplied to electrode heater 80 may be used to adjust the percentage ofthe optical signal which is directed to or “tapped by” optical waveguide61. For some applications the signal level or power level removed fromor “tapped by” waveguide 61 may be one-tenth of one percent (0.1%) orless. For other applications as much as ten percent (10%) of the signallevel or power level may be removed or “tapped by” waveguide 61. Opticalsignal level or power level which is “tapped by” waveguide 61 will oftendepend upon the sensitivity of the associated detector and the totalpower level of the optical signal communicated through waveguide 58.

Optical device 140 may also be referred to as a “variable tap” or“variable splitter.”. For example, by changing the amount of electricalcurrent supplied to electrode heater 80, the amount or percentage of anoptical signal directed from waveguide 58 to waveguide 61 may be varied.Optical device 140 may also be referred to as a “variable tap” becauseelectrical current may be supplied to one or more electrode heaters 80to tap or remove portions of an optical signal through waveguide 58 anddirect the tapped portion to one or more waveguides 61–68.

Optical device 140 may be used as an optical tap or optical splitterwhich can be varied by both the percentage of an optical signal which issplit or tapped from a waveguide and varied as to which waveguides 61–68receive the split or tapped signal. When certain types of informationare communicated through waveguide 58 a tap may be provided withwaveguide 61. For other types of information communicated throughwaveguide 58 a tap may be provided with only waveguide 68. Therefore,optical device 140 allows varying both the signal level or power levelwhich is removed from or tapped from a waveguide in the first array andalso allows varying which waveguide or waveguides in the second arrayreceives the split or tapped signal.

As previously noted, optical device 140 may also be used as an opticalattenuator. For example, electrical current may be provided to one ormore electrode heaters 80 to direct portions of an optical signaltraveling through waveguide 58 to one or more waveguides 61–68. Varyingthe amount of electrical current supplied to each electrode heater 80and varying the number of electrode heaters 80 may be used to adjust thepercentage of the optical signal traveling through waveguide 58 which isreduced or “attenuated” by directing portions of the optical signal toone or more waveguides 61–68. As discussed later in more detail, variouscontrol systems and/or monitoring systems may be provided such that boththe amount of electrical currents supplied to electrode heaters 80 maybe used to adjust the optical signal level such that the power level ofrespective optical signals exiting from output end 50B of waveguides51–58 are approximately equal with each other.

Optical device 140 may also be referred to as a “variable attenuator”.For example, by changing the amount of electrical currents applied toeach electrode heater 80, the amount or percentage of an optical signalwhich is attenuated within waveguides 51–58 may be varied. Opticaldevice 140 may also be used to provide “a dynamic variable tap” or a“dynamic variable optical attenuator” because the signal level of thetapped signal may be varied while the associated communication system isoperating and/or the amount of attenuation of an optical signal may bevaried while the associated communication system is operating.

FIGS. 3, 4, and 5 show various examples of waveguides which may beformed on a substrate using semiconductor fabrication techniques toproduce an optical device 140 incorporating teachings of the presentinvention. For the embodiments shown in FIGS. 3, 4, and 5, substrate 42may be part of a typical silicon wafer used in semiconductorfabrication. However, an optical device may be formed in accordance withteachings of the present invention on a wide variety of substrates andis not limited to use with only conventional silicon substrates.

Waveguides 51–58 and 61–68 of optical device 140 are preferably disposedin respective channels formed in a layer of top cladding. Waveguides51–58 and 61–68 may be formed from a wide variety of materials includingpolymers, polyimide, amorphous fluoropolymers such as Teflon® AF, amixture of silicon dioxide and polymeric materials, ion exchange andpolymer and fluorinated polyimide, perfluorocyclobutane (PFCB),bisbenzocyclobutene (CBC) and fluorinated cyclobutane compounds. Many ofthese materials are available from Dow Chemical Company. For someapplications a benzocyclobutene based polymer dielectrics such asCYCLOTENE™ Resins from The Dow Chemical Company may be used. CYCLOTENE™Resins are high-purity polymer solutions that have been developed formicroelectronics applications. The resins are derived from B-stagedbisbenzocyclobutene (BCB) monomers and are formulated as high-solids,low-viscosity solutions.

Teflon is a registered trademark of E. I. DuPont de Nemours and Company.Teflon AF, Teflon AF 1600, Teflon AF 2200 and Teflon AF 2400 areavailable from DuPont and other companies. For example, the top layermay be formed from Ultradel U 9120 polyimide having a refraction indexof 1.5397 and a core of Ultradel U 9020 polyimide having a refractionindex of 1.526. Ultradel is a trade name associated with polyimidematerials available from BP Amoco.

For some applications, the spacing between these channels may beapproximately eighty micrometers (80 mm). For other applications, thespacing between channels may be approximately one hundred twenty fivemicrometers (125 mm). The portions of the embodiments of the presentinvention shown in FIGS. 3, 4, and 5 include three channels designated44, 45 and 46. Each channel 44, 45 and 46 preferably has a generallyrectangular cross section with dimensions in the range of approximatelysix or seven micrometers (6 or 7 mm). Various features of the presentinvention will be described with respect to optical devices 140 a, 140 band 140 c as shown respectively in FIGS. 3, 4 and 5.

Optical device 140 a as shown in FIG. 3 preferably includes a layer 101a of silicon dioxide (SiO₂) disposed immediately adjacent to substrate42. For some applications, layer 101 a may have a thickness ofapproximately fifteen micrometers (15 mm) with an index of refraction ofapproximately 1.445. Waveguides 64, 65 and 66 may be formed on layer 101a from a combination of silicon dioxide and germanium oxide (SiO₂:GeO₂)with an index of refraction of approximately 1.4538. Second layer 102 ais preferably formed on first layer 101 a and waveguides 64, 65 and 66to provide channels 44, 45 and 46. Layer 102 a may also be referred toas “top cladding”. Respective waveguides 64, 65 and 66 are thus disposedin respective channels 44, 45 and 46. For the embodiment of the presentinvention as shown in FIG. 4 a, layer 102 a may be formed from Teflon AF1600 having an index of refraction of approximately 1.31. The thermaloptic coefficient of many polymers is generally less than zero. As aresult, when the temperature of such polymers is increased, thecorresponding index of refraction is reduced. Teflon AF 1600 representsone example of a polymer having the desired thermal optic coefficient.

Optical device 140 b as shown in FIG. 4 preferably includes first layer101 b formed from silicon dioxide having a thickness of approximately2.4 micrometers (2.4 mm). Second layer or top cladding 102 b may beformed from polymeric material such as Ultradel 9021 having an index ofrefraction of approximately 1.526. For the embodiment of the presentinvention as represented by optical switch 40 b, waveguides 64, 65 and66 may be formed from Ultradel 9120 having an index of refraction ofapproximately 1.5397.

Optical device 140 c as shown in FIG. 5 preferably includes first layer101 c formed from Teflon AF 240 having an index of refraction ofapproximately 1.29. Second layer or top cladding 102 c may be formedfrom Teflon AF 240 having an index of refraction of 1.29. The thicknessof first layer 101 c may be approximately five micrometers (5 mm).Waveguides 64, 65 and 66 may be formed from Teflon AF 160 having anindex of refraction of approximately 1.31.

FIG. 6 is a schematic drawing showing a plan view of one example ofoptical device 100 incorporating teachings of the present invention.Optical device 100 may be used as an optical signal tap or as part of anoptical signal attenuator. Optical device 100 preferably includes firstwaveguide 101 and second waveguide 102. Each waveguide 101 and 102 alsoincludes respective input ends “a” and output ends “b”. Although variousfeatures of the present invention will be described with respect to anoptical signal traveling from input end “a” to output end “b” of awaveguide, an optical device formed in accordance with teachings of thepresent invention may be satisfactorily used to switch or redirectoptical signals traveling in either direction through the waveguide.Also, Various features of the present invention will be described withrespect to tapping or attenuating an optical signal which is travelingthrough first waveguide 101. However, optical device 100 may also besatisfactorily used to tap or attenuate an optical signal travelingthrough second waveguide 102.

Input end 101 a of optical device 100 may be coupled with a respectivefiber optic cable. Output end 101 b of optical device 100 may be ispreferably coupled with another fiber optic cable or waveguide. Whenused as an optical signal tap or optical signal attenuator, input end102 a of optical device 100 is generally capped or not connect with asource of optical signals. Output end 102 b of each optical device 100may be coupled with an output port and another fiber optic cable orwaveguide.

When used as an optical signal tap or optical signal attenuator, opticalsignals will normally travel from input end 101 a through firstwaveguide 101 to output end 101 b. A portion of each optical signal maybe direct by optical device 100 to travel through second waveguide 102to an output port (not expressly shown) coupled with output end 102 b.Except for insertion losses and other minor losses associated with anoptical signal traveling through a waveguide, the optical power level ofan optical signal entering input end 101 a is approximately equal to thetotal optical power level exiting from output end 101 b plus output end102 b. Except for insertion losses and other minor losses associatedwith transmission of an optical signal through a waveguide, the totaloptical energy level or power level of optical signals communicatedthrough optical device 100 remains substantially constant.

Angle θ defined by intersection or junction 103 between first waveguide101 and second waveguide 102 is preferably selected to be in the rangeof approximately two degrees (2°) and eight degrees (8°). For at leastone application angle θ may be equal to approximately three degrees(3°). For other applications, angle θ is preferably approximately sixdegrees (6°). By forming optical device 100 with angle θ having a valuebetween approximately two degrees (2°) and eight degrees (8°), anoptical signal may travel through first waveguide 101 from input end 101a to output end 101 b without any significant perturbation or reflectionat intersection or junction 103 unless the index of refraction atjunction 103 is changed in accordance with teachings of the presentinvention. The index of refraction at junction 103 may be changed bythermooptic, electrooptic, magnetooptic, or acoustooptic effects.

Electrode heater 104 is preferably disposed adjacent to junction orintersection 103 to produce desired thermooptic effects. Electrodeheater 104, see FIGS. 6, 7 and 8, may be formed from various types ofmaterials including nickel chrome alloys (NiCr) and chromium gold(Cr/Au). Electrode heater 104 may be used to apply a desired amount ofheat to junction or intersection 103 to direct or deflect opticalsignals from first waveguide 101 to second waveguide 102. This functionof optical device 100 may be used to tap optical signals travelingthrough waveguide 101 and/or to attenuate such optical signals.

When electrical current is supplied to electrode heater 104, heatingwill occur in cladding layer 114 disposed between electrode heater 104and junction 103, see also FIG. 8, to produce a desired thermoopticeffect such as tapping and/or attenuation of an optical signal. Forexample, an optical signal may be directed to input end 101 a ofwaveguide 101. An appropriate amount of electrical current may besupplied to electrode heater 104 to provide a desired amount of heatingat intersection or junction 103 to direct (tap) a portion of the opticalsignal from waveguide 101 to waveguide 102 and output end 102 b. Tappingand an attenuation of optical signals will be discussed in more detailwith respect to the graphs shown in FIGS. 9 and 10.

The configuration and location of electrode heater 104 allows selectedheating of portions of waveguides 101 and 102 to form what may beconsidered as an imaginary, variable mirror disposed along alongitudinal center line of intersection 103. Heating cladding layer 114and portions of waveguides 101 and 102 at intersection 103 will permit achange in the refractive index such that selected amounts of internalrefraction may be achieved. In effect, heating by electrode heater 104will reflect or deflect at least a portion of light signals fromwaveguide 101 to waveguide 102.

For the embodiment of the present invention shown in FIGS. 6 and 7,current may flow from variable current source 106 through lead 108 toelectrode heater 104 and return through electrical lead 110 to ground112. The current flow through electrode heater 104 may be varied inaccordance with teachings of the present invention to allow switch 100to function as a variable optical attenuator. Waveguides 101 and 102,electrode heater 104, current source 106, electrical leads 108 and 110and ground 112 may be formed on a substrate using conventionalsemiconductor fabrication techniques.

FIG. 7 is a schematic drawing showing additional details associated withone embodiment of optical device 100. For example, low resistanceelectrical leads 108 and 110 are shown in more detail. For theembodiment of the present invention as shown in FIG. 7, electrode heater104 has a generally rectangular configuration defined in part by a pairof longitudinal edges 104 a and 104 b and a pair of lateral edges 104 cand 104 d. Longitudinal edges 104 a and 104 b may have a length ofapproximately two hundred fifty micrometers (250 μm). Lateral edges 104c and 104 d may have a length of approximately ten micrometers (10 μm).The thickness of electrode heater 104 is preferably very small, almostzero, as compared with the thickness of first waveguide 101 and secondwaveguide 102.

As shown in FIG. 8, a layer of cladding 114 is preferably disposedbetween first waveguide 101 and second waveguide 102 and junction orintersection 103. Longitudinal edge 104 b of electrode heater 104 ispreferably disposed on a line that corresponds generally with thelongitudinal center line of junction or intersection 103 between firstwaveguide 101 and second waveguide 102. For some applications, thevertical spacing or distance between electrode heater 104 and thecorresponding junction or intersection 103 is approximately fivemicrometers (5 μm) within a range of plus or minus 0.5 μm. The lateraloffset between longitudinal edge 104 b of electrode heater 104 and thecorresponding longitudinal center line of intersection 103 is preferablyless than 9.5 μm. When the offset between electrode heater 104 and therespective intersection 103 exceeds these limits, desired heating ofintersection or junction 103 and resulting internal reflection of anoptical signal traveling therethrough may not occur as desired.

For the embodiment of the present invention shown in FIG. 8, opticaldevice 100 preferably includes layer 118 disposed immediately adjacentto substrate 116. Layer 118 may be formed from various types of materialsuch as silicon dioxide (SiO₂), or other materials such as Teflon AF240. First waveguide 101 and second waveguide 102 may be formed fromvarious types of material such as a combination of silicon dioxide andgermanium oxide (SiO2:GeO2) with an index of refraction of approximately1.4538. For some applications, layer 118 may have a thickness ofapproximately fifteen micrometers (15 μm) with an index of refraction ofapproximately 1.445.

Waveguides 101 and 102 may be formed on layer 118 and disposed inrespective channels 115 and 117 formed in cladding layer 114. For oneembodiment channels 115 and 117 preferably have a generally rectangularcross section with dimensions in the range of approximately of six orseven micrometers (6 or 7 μm). Layer 114 may sometimes be referred to as“top cladding”. Layer 114 may be formed from Teflon AF 1600 having anindex of refraction of approximately 1.31. The thermooptic coefficientof many polymers is generally less than zero. As a result, when thetemperature of such polymers is increased, the corresponding index ofrefraction is reduced. Teflon AF 1600 represents one example of apolymer having the desired thermooptic coefficient. Perfluorocyclobutane(PFCB) is another example of a polymer having the desired thermopticcoefficient.

For other applications first layer 118 may be formed from silicondioxide having a thickness of approximately 2.4 micrometers (2.4 μm).Second layer or top cladding 114 may be formed from polymeric materialsuch as Ultradel 9021 having an index of refraction of approximately1.526. Waveguides 101 and 102 may be formed from Ultradel 9120 having anindex of refraction of approximately 1.5397.

For still other applications first layer 118 may be formed from TeflonAF 240 having an index of refraction of approximately 1.29. Second layeror top cladding 114 may be formed from Teflon AF 240 having an index ofrefraction of 1.29. The thickness of first layer 118 may beapproximately five micrometers (5 μm). Waveguides 101 and 102 may beformed from Teflon AF 160 having an index of refraction of approximately1.31.

Waveguides 101 and 102 may be formed from a wide variety of materialsincluding polyimide, Teflon, a mixture of silicon dioxide and polymer,ion exchange and polymer and fluorinated polyimide. Layer 114 may beformed from Ultradel polymer U 9120 having a refraction index of 1.5397and waveguides 101 and 102 of Ultradel U 9020 having a refraction indexof 1.526.

FIG. 9 is a graph showing optical signal level versus time for a givencurrent flow through electrode heater 104. For one example of opticaldevice 100, optical signal level was measured at output end 101 b offirst guide 101 versus time in seconds at a substantially constantcurrent flow through electrode heater 104. The current supplied toelectrode heater 104 was maintained at approximately forty milliamps forthirty six hundred (3600) seconds or sixty (60) minutes.

FIG. 10 is a graph showing output power or signal level in decibels (dB)measured at output end 101 b of waveguide 101 versus electrical currentflow through electrode heater 104. An optical signal with constant poweror signal level was supplied to input end 101 a of waveguide 101 whileelectric current flow to electrode heater 104 was varied in accordancewith teachings of the present invention. As previously noted, the powerlevel or signal level of an optical signal entering input end 101 a ofwaveguide 101 is generally equal to the combined power level or signallevel of optical signals exiting from output end 102 b of waveguide 102and output end 101 b of waveguide 101. Therefore, a similar measurementof output power or signal level measured at output end 102 b ofwaveguide 102 would be approximately the inverse of the graph shown inFIG. 10.

The graphical information shown in FIG. 10 demonstrates that increasingcurrent flow through electrode heater 104 of optical device 100 may beused to attenuate or decrease the output power or signal level of anoptical signal traveling between input end 101 a and output end 101 b ofwaveguide 101. In the same manner, the output power or signal level ofthe portion of the optical signal directed to output end 102 b ofwaveguide 102 may be selectively increased or decreased. Attenuation ofan optical signal at output end 101 b or increase in optical signal atoutput end 102 b is particularly significant between approximatelytwenty-two milliamps and forty milliamps.

FIG. 11 is a schematic drawing which shows a portion of opticalattenuator 160 formed in accordance with teachings of the presentinvention. Dynamic, variable optical attenuator 160 may include multiplewaveguides 162 with optical signals traveling therethrough. For purposesof describing various features of the present invention the waveguidesare designated as 162 a and 162 b. Additional waveguides 164 preferableintersect with and form respective junctions 70. For purposes ofdescribing various features of the present invention waveguides 164, asshown in FIG. 11 have been designated 164 a, 164 b, 164 c and 164 d. Theassociated electrode heaters 80 and junctions 70 have similardesignations of “a,b,c, and d”.

During operation of dynamic, variable optical attenuator 160, waveguide164 b and electrode heater 80 b preferably cooperate with each other toremove or tap a selected portion of the optical signal traveling throughwaveguide 162 a. The output portion of waveguide 164 b may be opticallycoupled with an appropriate detector or monitor (not expressly shown) todetermine various characteristics associated with the optical signal orsignals traveling through waveguide 162 a. If the intensity or signallevel within waveguide 162 a exceeds a desired value, an appropriateamount of electrical current may be provided to electrode 80 a such thata portion of the optical signal traveling through waveguide 162 a willbe directed to waveguide 164 a and dumped.

Waveguide 164 d and associated electrode 80 d provide a similarcapability to tap or monitor optical signals communicated throughwaveguide 162 b. When the intensity or power level of such signalsexceeds a pre-selected value, electrical current may be supplied toelectrode heater 80 c to direct a portion of the optical signaltraveling through waveguide 162 b to waveguide 164 c. Thus, variableoptical attenuator 160 may be used to maintain substantially the samepower level with respect to optical signals traveling through waveguides162 a and 162 b.

Dynamic, variable optical attenuator 60 incorporating teachings of thepresent invention is shown in FIG. 12. The various components associatedwith Dynamic, variable optical attenuator 260 may be formed on asemiconductor substrate as previously described with respect to opticaldevices 100 and 140. For the embodiment of the present invention asshown in FIG. 12 dynamic, variable optical attenuator includes 20waveguides designated 301 through 320. Fiber optic cables and/or otherwaveguides may be optically coupled with the input end and the outputend of each waveguide 201 through 220.

A second array of waveguides designated 301 through 340 may also bedisposed on the same substrate to intersect with the first set ofwaveguides 201–202. Each waveguide 201 through 220 preferable intersectswith at least two waveguides of the second set. For example, waveguide201 preferably intersects with at least waveguide 301 and 302.Respective electrode heaters 80 are preferably disposed on theintersection or junction between waveguide 201 and waveguides 301 and302. For some applications all of the waveguides in the first set orarray (201–220) will intersect with each of the waveguides in the secondarray or second set (301–340). In a manner similar to optical device140. For the embodiment of the present invention as shown in FIG. 12dynamic variable optical attenuator 260 may be described as a 20×40array.

Waveguide 302 and its associated electrode heater 30 may function as atap to monitor optical signals traveling through waveguide 201.Waveguide 302 may be connected with optical detector 400 by fiber opticcable or other suitable waveguide 401. In a similar manner waveguide 402may be used to optically couple waveguide 304 with detector 400.

Detector 400 may be used to measure various characteristics of theoptical signals traveling through the respective waveguides 201–220. Oneof these characteristics may be signal level or power level of theassociated optical signal. Electrical signals corresponding with thesecharacteristics may then be transmitted to heater controller 500. Basedon the information collected by detector 400, heater controller 500 mayvary the electric current flow directed to each electrode heater 80 tovary the amount of the optical signal which is tapped by waveguide 302.Also, heater controller 400 may vary the electrical signal provided tothe respective electrode heater 80 to vary the portion of the opticalsignal which may be dumped from waveguide 201 by waveguide 301. Detector400 and heater controller 500 may perform the same functions for therespective tap and attenuator associated with each waveguide 201–220.Thus variable dynamic attenuator 260 may vary the attenuation and alsothe tapping of optical signals communicated through waveguides 201–220while the associated communication system or network remains inoperation.

FIG. 13 illustrates an optical communication system which may includevariable optical attenuators and optical taps formed in accordance withthe teachings of the present invention. The system, illustratedgenerally at 1400, includes a plurality of regions operable tocommunicate information via a fiber optic network. Network 1400 includesa region A 1401, region B 1402, region C 1403, and region D 1404optically coupled to an N×N array 1405. Region D is further coupled toregion E 1407, and region F 1408 via N×N array 1406. Server 1409 iscoupled to region F 1408 and N×N array 1410. N×N array 1410 is alsocoupled to first client terminal 1411, second client terminal 1412, andthird client terminal 1413.

Fiber optic cable 1420 having a plurality of fiber optic waveguides 1421may be coupled between regions via an N×N array. For example, region A1401 may be coupled to N×N array 1405 via a fiber optic cable having10,000 channels or fiber optic waveguides. Additionally, region 1404 maybe coupled to N×N array 1405 via a fiber optic cable having 1,000channels or fiber optic waveguides.

Network 1400 advantageously provides for high capacity fiber opticutilization operable to communicate optical signals at high transmissioncapacities. In one embodiment, communication between each region may beobserved as a “long haul” communication, a “regional” communication, a“metro” communication, and “user” communication regions. As such, N×Narrays 1405, 1506 and 1410 provide communication between the pluralityof regions such that optical signals may be communicated to desirabledestinations. For example, N×N array 1405 may include optical outputsand optical inputs between region A 1401 and region B 1402. As such, acontrol circuit may provide a control signal such that an optical signalmay be attenuated or taped using optical devices 140.

In another embodiment network 1400 may be operable to communicate orswitch optical signals between server 1409 and client terminals 1411,1412 and 1413. For example, a control circuit (not shown) operablycoupled to N×N array of optical device 140 may tap and/or attenuateoptical signals communicated between server 1409 client terminals 1411,1412 and 1413 by providing appropriate electrical currents to heatselected junctions between two waveguides such that an optical signalincident to N×N array 1410 may be tapped between a client terminal andserver 1409.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalternations can be made herein without departing from the spirit andscope of the invention as defined by the following claims.

1. An optical system, comprising: at least one of: an opticalmultiplexer; an optical demultiplexer; and, an optical amplifier; and anoptical device configured for communication with one or more of theoptical multiplexer, the optical demultiplexer and the opticalamplifier, the optical device comprising: a substrate; a first waveguidearray disposed proximate the substrate; and a second waveguide arraydisposed proximate the substrate so that at least a portion of thesecond waveguide array intersects at least a portion of the firstwaveguide array at a predetermined angle, the first and secondwaveguides collectively defining at least one junction having anassociated variable index of refraction.
 2. The optical system asrecited in claim 1, wherein the number of waveguides in the first andsecond waveguide arrays is the same.
 3. The optical system as recited inclaim 1, wherein the number of waveguides in the first and secondwaveguide arrays is different.
 4. The optical system as recited in claim1, wherein at least some of the waveguides in the first waveguide arrayare substantially parallel to each other.
 5. The optical system asrecited in claim 1, wherein at least some of the waveguides in thesecond waveguide array are substantially parallel to each other.
 6. Theoptical system as recited in claim 1, wherein an angle defined by anintersection between the first and second waveguide arrays is in a rangeof about 2 degrees to about 8 degrees.
 7. The optical system as recitedin claim 1, wherein the index of refraction is variable in response toat least one of the following: an electro-optic effect; a magneto-opticeffect; and, an acousto-optic effect.
 8. The optical system as recitedin claim 1, wherein the variable index of refraction facilitatesvariation to a percentage of an optical signal diverted from aparticular waveguide.
 9. The optical system as recited in claim 1,wherein the variable index of refraction facilitates designation of aparticular waveguide for receipt of a diverted signal.
 10. The opticalsystem as recited in claim 1, wherein the optical device comprises oneof: an optical attenuator; an optical tap; and, an optical splitter. 11.The optical system as recited in claim 1, further comprising a heaterlocated proximate the at least one junction.
 12. The optical system asrecited in claim 1, further comprising a backplane configured andarranged to facilitate optical coupling of the optical device with oneor more of: the optical multiplexer; the optical demultiplexer; and, theoptical amplifier.
 13. The optical system as recited in claim 1, furthercomprising a first material layer interposed between the substrate andthe first and second waveguide arrays.
 14. An optical device,comprising: a substrate; a first material layer disposed on thesubstrate; first and second waveguides disposed on the first materiallayer and intersecting each other so as to define a junction having anassociated variable index of refraction; and a second material layerdisposed on the first and second waveguides; and wherein the substratesubstantially comprises silicon.
 15. The optical device as recited inclaim 14, further comprising a heater located proximate the junction.16. The optical device as recited in claim 14, wherein the firstmaterial layer disposed on the substrate substantially comprises silicondioxide (SiO₂).
 17. The optical device as recited in claim 14, whereinat least one of the first and second waveguides substantially comprisesa combination of silicon dioxide (SiO₂) and germanium oxide(GeO₂). 18.The optical device as recited in claim 14, wherein the second materiallayer defines respective first and second channels wherein the first andsecond waveguides are substantially disposed.
 19. The optical device asrecited in claim 14, wherein an angle defined by an intersection betweenthe first and second waveguides is in a range of about 2 degrees toabout 8 degrees.
 20. The optical device as recited in claim 14, whereinthe second material layer comprises a top cladding.
 21. The opticaldevice as recited in claim 14, wherein the second material layersubstantially comprises a polymeric material.
 22. The optical device asrecited in claim 14, wherein an index of refraction of the firstmaterial layer is substantially the same as an index of refraction ofthe second material layer.
 23. The optical device as recited in claim14, wherein the waveguides have an index of refraction greater than anindex of refraction of at least one of the first and second materiallayers.
 24. The optical device as recited in claim 14, wherein an indexof refraction of at least one of the material layers decreases inresponse to an increase in temperature.
 25. The optical device asrecited in claim 14, wherein the index of refraction varies with changesin temperature.
 26. The optical device as recited in claim 14, whereinthe optical device comprises one of: an optical attenuator; an opticaltap; and, an optical splitter.
 27. The optical device as recited inclaim 14, wherein the variable index of refraction facilitates variationto a percentage of an optical signal diverted from a particularwaveguide.
 28. The optical device as recited in claim 14, wherein thevariable index of refraction facilitates designation of a particularwaveguide for receipt of a diverted signal.
 29. A method for forming anoptical device, the method comprising: forming a substrate; forming afirst material layer on the substrate; forming first and secondwaveguides on the first material layer such that the first and secondwaveguides intersect each other and define a junction; and forming asecond material layer on the first and second waveguides; and whereinthe substrate substantially comprises silicon.
 30. The method as recitedin claim 29, wherein the second material layer comprises a top cladding.31. The method as recited in claim 29, wherein the second material layersubstantially comprises a polymeric material.
 32. The method as recitedin claim 29, wherein the first material layer disposed on the substratesubstantially comprises silicon dioxide (SiO₂).
 33. The method asrecited in claim 29, wherein at least one of the first and secondwaveguides substantially comprises a combination of silicon dioxide(SiO₂) and germanium oxide(GeO₂).
 34. The method as recited in claim 29,wherein the second material layer is formed so as to define respectivefirst and second channels wherein the first and second waveguides aresubstantially disposed.
 35. The method as recited in claim 29, whereinthe waveguides are formed so that an angle defined by an intersectionbetween the first and second waveguides is in a range of about 2 degreesto about 8 degrees.
 36. An optical device, comprising: substrate; firstmaterial layer disposed on the substrate; first waveguide array disposedon the first material layer; second waveguide array disposed on thefirst material layer so that at least a portion of the second waveguidearray intersects at least a portion of the first waveguide array at apredetermined angle, the first and second waveguides collectivelydefining at least one junction having an associated variable index ofrefraction; and a second material layer disposed on the first and secondwaveguide arrays.
 37. The optical device as recited in claim 36, whereinthe variable index of refraction facilitates variation to a percentageof an optical signal diverted from a particular waveguide.
 38. Theoptical device as recited in claim 36, wherein the variable index ofrefraction facilitates designation of a particular waveguide for receiptof a diverted signal.